多孔石墨烯及其复合材料制备锂离子电池负极材料的研究

发布时间：2018-07-05 13:28

本文选题：多孔石墨烯 + 碳纳米管　；参考：《中国石油大学(北京)》2016年博士论文

【摘要】：近年来,人们对清洁无污染的新型能源越来越关注。锂离子电池作为新能源的一种,以其高的能量密度、长的循环寿命及无记忆效应等优点被广泛应用于各种便携式电子设备,如手机、笔记本电脑和相机等。同时,锂离子电池在电动汽车领域也表现出了广阔的应用前景,使得具有高能量密度和高功率密度的锂离子电池成为各国竞相开发的热点。电极材料是决定锂离子电池性能的重要因素之一。在负极材料方面,目前商业化的负极材料主要为石墨,其理论比容量只有372 m Ah g~(-1),远远不能满足电动设备的实际需求。因此,设计和制备高性能的锂离子电池负极材料具有重要的战略意义。石墨烯作为一种新型的碳材料,因其具有超大的比表面积和超高的导电性等优异的性质,在能源、材料和电化学等领域都有很大的应用前景。因此,本文以石墨烯基材料为研究对象,以提高锂离子电池的能量密度、功率密度及循环寿命为目的,设计和制备了一系列高性能的石墨烯基锂离子电池负极材料。具体内容如下:(1)采用化学气相沉积法,调控生长制备了具有大比表面积(1620 m g)的多孔石墨烯材料。多孔石墨烯的多孔结构和超高的导电性使其实现了高效的锂离子和电子传输与反应。因此,多孔石墨烯表现出优异的循环性能和倍率性能。在电流密度150 m A g~(-1)下循环50次后,多孔石墨烯的充电比容量从823 m Ah g~(-1)提高到1247 m Ah g~(-1)(提高了34%);在电流密度1000 m A g~(-1)下的充电比容量仍高达455 m Ah g~(-1)。(2)采用化学气相沉积法,制备了具有三维结构的碳纳米管-多孔石墨烯复合材料。多孔石墨烯的存在有效地抑制了碳纳米管的团聚,同时该复合材料中Fe3C纳米颗粒的存在,使其具有了超顺磁性,可以应用于磁性药物载体等多个领域。和多孔石墨烯材料相比,碳纳米管-多孔石墨烯复合材料具有更丰富的多孔结构,但是由于碳纳米管的存在,使其比表面积要比多孔石墨烯小,所以不能提供更多的储锂位点,因此其储锂性能不如多孔石墨烯材料。(3)多孔石墨烯材料表现出了优异的电化学性能,但其超大的比表面积使其首次不可逆容量比较大,因此采用液相沉积法调控制备了Co3O4-多孔石墨烯复合材料。Co3O4纳米颗粒一方面具有高的理论比容量(890 m Ah g~(-1)),另一方面可以有效地防止多孔石墨烯的堆积和聚并,同时Co3O4纳米颗粒可以嵌入到多孔石墨烯的孔结构中,降低了复合材料的比表面积,从而有效地降低了不可逆容量的产生。多孔石墨烯一方面可以缓解Co3O4纳米颗粒充放电过程中体积的变化,另一方面其三维多孔网状结构加速了锂离子的传输,同时其本身是电子的优良导体,加速了电子传输。因此,Co3O4-多孔石墨烯复合材料表现出高的质量比容量(单位质量的活性物质的充电容量)和体积比容量(单位体积的活性物质的充电容量)。在电流密度150 m A g~(-1)下循环50次后,70%Co-PGN复合材料(复合材料中Co3O4的质量分数为70%)的质量比容量由1336 m Ah g~(-1)上升到1439 m Ah g~(-1);当电流密度上升到1000 m A g~(-1)时,70%Co-PGN复合材料相应的质量比容量仍然高达1072m Ah g~(-1)。同时,70%Co-PGN复合材料具有高的体积比容量(在电流密度50和1000m A g~(-1)下,70%Co-PGN复合材料的体积比容量分别为1993和1678 m Ah cm-3,远高于多孔石墨烯的体积比容量)。(4)采用液相沉积法制备了具有核@孔@壳结构的Fe_2O_3-多孔石墨烯复合材料。不同于Co3O4-多孔石墨烯复合结构,在该复合结构中,Fe_2O_3纳米颗粒是通过改变多孔石墨烯的表面结构来提高复合材料的电化学储能性能。Fe_2O_3纳米颗粒可以催化分解复合材料表面形成的SEI膜,从而提高其电化学性能。因此,Fe_2O_3-多孔石墨烯复合材料表现出优异的循环性能和倍率性能。在电流密度150 m A g~(-1)下循环50次后,10%Fe-PGN复合材料(复合材料中Fe_2O_3的质量分数为10%)的充电比容量由1289 m Ah g~(-1)上升到1567 m Ah g~(-1);在电流密度1000 m A g~(-1)下循环100次后,10%Fe-PGN复合材料的充电比容量由814 m Ah g~(-1)上升到883 mAh g~(-1)。
[Abstract]:In recent years, people have paid more and more attention to clean and non polluting new energy sources. As a new energy source, lithium ion batteries have been widely used in all kinds of portable electronic devices, such as mobile phones, notebook electroencephalograph and cameras, etc., with their high energy density, long cycle life and memory free effect. The domain also shows broad application prospects, making lithium ion batteries with high energy density and high power density become the hot spots in the development of various countries. Electrode material is one of the important factors to determine the performance of lithium ion batteries. In the negative electrode material, the commercialized negative material is mainly graphite, its theoretical specific capacity is only 372 m. Ah g~ (-1) can not meet the actual demand of electric equipment. Therefore, the design and preparation of high performance anode materials for lithium ion batteries is of great strategic significance. As a new type of carbon material, graphene has excellent properties, such as high specific surface area and ultra-high conductivity, in the fields of energy, materials and electrochemistry. In order to improve the energy density, power density and cycle life of lithium ion batteries, a series of high performance graphite anode materials for lithium ion batteries are designed and prepared in this paper. The specific contents are as follows: (1) chemical vapor deposition (CVD) is used to regulate and control the growth of the lithium ion battery. Porous graphene material with large specific surface area (1620 m g). Porous graphene's porous structure and ultra-high conductivity make it achieve high efficiency of lithium ion and electron transfer and reaction. Therefore, porous graphene shows excellent cycling performance and multiplying performance. After 50 cycles under the current density of 150 m A g~ (-1), porous graphene The charge specific capacity is increased from 823 m Ah g~ (-1) to 1247 m Ah g~ (-1) (increased by 34%), and the charge specific capacity at 1000 m A g~ (-1) is still up to 455. (2) the carbon nanotube porous graphene composite with three-dimensional structure is prepared by chemical vapor deposition. The presence of porous graphene effectively inhibits carbon The presence of Fe3C nanoparticles in the composite makes it superparamagnetic and can be used in many fields, such as magnetic drug carriers. Compared with the porous graphene material, the carbon nanotube - porous graphene composite has a more abundant porous structure, but the presence of carbon nanotubes makes it more than the surface. The product is smaller than porous graphene, so it can not provide more lithium storage sites, so its lithium storage performance is not as good as porous graphene material. (3) porous graphene exhibits excellent electrochemical performance, but its large specific surface area makes its initial irreversible capacity larger, so Co3O4- multi Kong Shi is controlled by liquid phase deposition. .Co3O4 nanoparticles have high theoretical specific capacity (890 m Ah g~ (-1)) on the one hand, on the other hand, it can effectively prevent the accumulation and accumulation of porous graphene, and Co3O4 nanoparticles can be embedded in the pore structure of porous graphene, reducing the specific surface area of the composite, thus effectively reducing the irreversible capacity. On the one hand, porous graphene can alleviate the volume change in the charge discharge process of Co3O4 nanoparticles, on the other hand, the three-dimensional porous network structure accelerates the transmission of lithium ion. At the same time, it is an excellent conductor of the electron and accelerates the electron transport. Therefore, the Co3O4- polypore graphene composite exhibits high mass ratio capacity. (unit mass active material charging capacity) and volume specific capacity (charge capacity per unit volume of active substance). After 50 cycles under 150 m A g~ (-1) current density, the mass ratio of 70%Co-PGN composites (the mass fraction of Co3O4 in composite materials is 70%) rises from 1336 m Ah g~ (-1) to 1439 m Ah. When up to 1000 m A g~ (-1), the corresponding mass specific capacity of 70%Co-PGN composites is still as high as 1072m Ah g~ (-1). At the same time, the 70%Co-PGN composite has a high volume specific capacity (at the current density of 50 and 1000m A), the volume specific capacity of the composite material is 1993 and 1678, far higher than the volume ratio of the porous graphene. (4) (4) a porous graphene composite with a core @ shell structure is prepared by liquid deposition. Different from the composite structure of Co3O4- porous graphene, the Fe_2O_3 nanoparticles can improve the electrochemical energy storage properties of the composite by changing the surface structure of the porous graphene to improve the electrochemical energy storage properties of.Fe_2O_3 nanoparticles. It can catalyze the decomposition of the SEI film formed on the surface of the composite to improve its electrochemical performance. Therefore, the Fe_2O_3- porous graphene composite exhibits excellent cycling performance and multiplying performance. After 50 cycles under the current density of 150 m A g~ (-1), the specific capacitance of the 10%Fe-PGN composite (the mass fraction of Fe_2O_3 in the composite is 10%) The quantity rises from 1289 m Ah g~ (-1) to 1567 m Ah g~ (-1); after 100 cycles under the current density of 1000 m A g~ (-1), the charge ratio of the composite increases from 814 to 883.
【学位授予单位】：中国石油大学(北京)
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ127.11;TB33;TM912

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